The harlequin has a distinctive head marking
A UK-wide survey is being launched to track an alien ladybird that threatens the existence of native species.
The harlequin (Harmonia axyridis) was first spotted in Britain in September last year and is largely confined to the South East.
But the invader is a voracious predator that easily out-competes home bugs for food and is likely to spread north.
Scientists want gardeners and wildlife enthusiasts to report sightings of the pest to www.harlequin-survey.org.
The launch of the survey, which takes place at London's Natural History Museum, is timed to coincide with the coming of milder spring weather.
"I understand from the Met Office that we could have temperatures of 17-19 Celsius by the end of the week and that will wake the ladybirds up," Dr Michael Majerus, of Cambridge University, told the BBC News website.
"We're hoping not only to monitor the harlequin and its impact but also to use the whole study as a model for how to deal with invasive species."
Originally from Asia, the harlequin was probably imported into the UK on plants that came in from continental Europe.
Sightings of the beetle have been mainly restricted to the south east, extending to Hampshire in the west and Norfolk in the north.
The insect has a huge appetite for greenfly, leaving little for native ladybirds who then starve.
Worse still, the harlequin will turn on other ladybirds if food resources diminish for the whole population. The invader will also prey on other types of insects, eating butterfly eggs, caterpillars and lacewing larvae.
Harlequin ladybirds are also partial to soft fruit, particularly pears.
"The harlequin may sound like a bit of a jester but there is nothing funny about it at all," said Matt Shardlow, from invertebrate conservation group Buglife.
"There're a whole lot of problems it will bring with it. It out-competes native species and eats them.
"Everyone should be vigilant for the species and record where it is."
"I'm afraid it's damage limitation now - but hopefully we may be able to develop a pheromone-specific trap," explained Dr Majerus.
"They are attracted in large swarms to the same place in winter; we think they do it by scent. If it's a reasonably species-specific scent then we may be able to develop a box trap using the scent as a bait."
The harlequin problem began in North America where their ability to take out other populations of insects made them an attractive bio-control agent.
But in the space of less than 20 years, they have now come to dominate their niche and are by far the commonest ladybird species.
In France, Belgium and Holland, their numbers are also soaring annually.
HOW TO SPOT A HARLEQUIN
Tends to be rounder in shape than most UK native species
About 5-8mm in size - similar to the common seven spot
It has a white plate with a big black M-shaped marking on it, just behind the head
Sighted bugs can be orange with between 15 and 20 spots
Others may be black with two orange or red spots
Some also seen to be black with four orange or red spots
The fear is they will sweep aside many of the 46 species from the ladybird family (Coccinellidae) in Britain.
The survey is being organised by researchers from the University of Cambridge, Anglia Polytechnic University, the Centre for Ecology and Hydrology, the Natural History Museum and The Wildlife Trusts.
The call is for all gardeners, farmers, wildlife enthusiasts and anyone with a love of ladybirds to examine trees, bushes and plants and record all ladybirds, including the harlequin, they find.
Surveyors are asked to report any sightings of the harlequin ladybird, including where it was found (using a grid reference or postcode), the date and how many ladybirds there were. A photograph of the ladybird would also help verification of each find.
This information should go to www.harlequin-survey.org. All other ladybird sightings should be reported to www.ladybird-survey.org.
Now is the time that ladybirds will start to wake up and begin looking for partners with which to mate. Ladybirds are normally found wherever there is food.
Any plant, shrub or tree with greenfly or scale insects may attract harlequins.